[Qgis-developer] QGIS crash removing group containing rasters

[Alessandro Pasotti]

On Sat, Sep 3, 2016 at 5:09 PM, Luca Congedo <
semiautomatic.blogger at gmail.com> wrote:

> I think I found the cause of the issue when trying to remove a layer that
> was already removed.
> To reproduce in Python console:
> # add raster
> l1 = qgis.utils.iface.addRasterLayer("C:\Users\a\Desktop\LC81900312013105LGN01_B2.tif",
> "raster1")
>
> remove manually the raster
>
> # try to remove the raster
> QgsMapLayerRegistry.instance().removeMapLayer(l1.id())
>
> QGIS crashes
>
> Cheers,
> Luca
>
>
>

Hi, I believe that this is not something we can fix easily: removing the
layer from the map registry deletes the layer removing the object from
memory but the python variable still points to an object that was deleted,
of course it crashes.

There are many other similar ways you can make QGIS crash, this is due to
the nature of Python - C++ bindings and there is not much we can do, the
Python programmers should take care to avoid such potentially dangerous
situations.

You might want to use the sip API directly if you want to check for deleted
objects:
http://pyqt.sourceforge.net/Docs/sip4/python_api.html

Hope this helps.

Cheers



> 2016-09-03 11:57 GMT+02:00 Luca Congedo <semiautomatic.blogger at gmail.com>:
>
>> Hi Matthias,
>>
>> yes, it happens in Windows when removing the group manually (it seems
>> that Linux is not affected).
>> I had a button in the plugin for removing the temporary rasters which I
>> have now disabled in a plugin update.
>>
>> Luca
>>
>>
>> 2016-09-03 11:53 GMT+02:00 Matthias Kuhn <matthias at opengis.ch>:
>>
>>> Hi Luca,
>>>
>>> does it also happen when you do the same process manually?
>>>
>>> Matthias
>>>
>>> On 09/03/2016 11:43 AM, Luca Congedo wrote:
>>> > Hello everybody,
>>> >
>>> > removing a group (created by the Semi-Automatic Classification Plugin)
>>> > containing rasters from QGIS layers causes a crash.
>>> > To reproduce, if you create 2 or more classification previews with the
>>> > Semi-Automatic Classification Plugin and then remove the group
>>> > 'Class_temp_group' from the layers.
>>> > Is there anything I can do at the plugin level, or should I open a
>>> ticket?
>>> >
>>> > Thank you,
>>> > Luca
>>> >
>>> >
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>>
>>
>
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-- 
Alessandro Pasotti
w3:   www.itopen.it
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